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United States Patent |
5,669,458
|
Anders
|
September 23, 1997
|
Rotary jar
Abstract
A rotary jar is described that is part of a drill string and includes a
mandrel and an anvil that move longitudinally in opposite directions to
deliver a sharp upward or downward blow that is transmitted to a fish,
which may be a separate tool or a portion of the drill string that is
stuck in the well bore in an effort to free the fish or the stuck portion
of the drill pipe. The mandrel carries rollers that move through
longitudinally extending grooves when the jars are tripped. In the jars of
this invention, the grooves follow a serpentine path to cause the mandrel
to transmit a torsional force on the fish to try to rotate the fish as
well as providing an upward or downward blow.
Inventors:
|
Anders; Edward O. (106 Saint Andrews Loop, Kerrville, TX 78028)
|
Appl. No.:
|
609536 |
Filed:
|
March 1, 1996 |
Current U.S. Class: |
175/299; 166/178; 175/304 |
Intern'l Class: |
E21B 031/107 |
Field of Search: |
166/178
175/299,302,304,305,306
|
References Cited
U.S. Patent Documents
2096135 | Oct., 1937 | Raymond | 175/303.
|
2585318 | Feb., 1952 | Howard | 175/304.
|
2597414 | May., 1952 | Waggener | 175/302.
|
3208541 | Sep., 1965 | Lawrence | 175/299.
|
3233690 | Feb., 1966 | Lawrence | 175/302.
|
3709478 | Jan., 1973 | Kisling | 267/137.
|
3853187 | Dec., 1974 | Sutliff et al. | 175/297.
|
3963081 | Jun., 1976 | Anderson et al. | 175/304.
|
4186807 | Feb., 1980 | Sutliff et al. | 175/302.
|
4270620 | Jun., 1981 | Lawrence | 175/322.
|
4298078 | Nov., 1981 | Lawrence | 175/72.
|
4376468 | Mar., 1983 | Clark | 175/304.
|
4526241 | Jul., 1985 | Anders | 175/76.
|
4665998 | May., 1987 | Burton | 175/299.
|
4688649 | Aug., 1987 | Buck | 175/299.
|
Primary Examiner: Bagnell; David J.
Attorney, Agent or Firm: Vaden, Eickenroht & Thompson, L.L.P.
Claims
What is claimed:
1. In a rotary jar for connecting in a pipe string to produce a sharp
upward or downward force on the pipe string when the pipe string becomes
stuck in a well bore said jar comprising, an inner tubular mandrel member
and an outer tubular anvil member for connecting in a pipe string for
limited longitudinal movement relative to each other, impact shoulders on
the members limit the relative longitudinal movement of the members, a
plurality of laterally spaced rollers attached to the outer surface of the
mandrel, longitudinally extending grooves on the inner surface of the
anvil, each groove intersecting a U-shaped laterally extending notch
formed with curved outwardly flaring walls on the inner surface of the
mandrel, and resilient means urging the tubular members to rotate relative
to each other in the direction to move the rollers into the U-shaped
notches and to allow the roller means to move out of the U-shaped notches
when a longitudinal force is imposed on the jar sufficient for the flared
walls of the U-shaped notches to provide a lateral component of force on
the rollers that will overcome the force of the resilient means and move
the rollers out of the U-shaped notches into the longitudinally extending
grooves allowing the mandrel to move longitudinally relative to the anvil
until the impact shoulders engage and produce a sharp increase in the
force exerted by the string when the string is stuck in the hole, the
improvement comprising longitudinally extending serpentine grooves that
convert a portion of the relative longitudinal motion of the mandrel and
the anvil into angular motion tending to rotate the anvil back and forth
relative to the mandrel.
2. The jar of claim 1 in which said serpentine groove is sinusoidal.
3. The jar of claim 1 in which said resilient means are a plurality of
longitudinally spaced torque springs connecting the inner and outer
tubular members.
4. The jar of claim 1 further including, a torque dissipating sub for
connecting to the upper end of the mandrel to prevent the left hand torque
imposed on the mandrel from being transmitted to tool joints above the
jars said torque dissipating subcomprising inner and outer tubular
members, means for connecting the inner tubular member of the assembly to
the mandrel of the jar, means for connecting the outer tubular member to
the pipe string, an annular cavity between the inner and outer members,
and clutch plates positioned in the cavity to prevent relative right hand
rotation between the inner and outer tubular members to thereby transmit
right hand torque to the jars and the pipe string below the jars sub and
the mandrel and allowing left hand rotation of the inner tubular member
relative to the outer tubular member to prevent left hand torque from
being transmitted to the tool joint above the sub.
5. The jar of claim 1 further comprising a torque dissipating sub for
attaching in the pipe string above the jar and to the mandrel of the jar,
said assembly having inner and outer tubular members rotationally movable
relative to each other, means for connecting the inner tubular member of
the assembly to the mandrel of the jar, means for connecting the anvil to
the pipe string, a coil spring encircling the inner member having one end
connected to the inner surface of the outer tubular member and the other
end connected to the outer surface of the inner tubular member of the
assembly to prevent relative right hand rotation between the pipe string
and the jars while allowing limited left hand rotation of the pipe string.
Description
BACKGROUND OF THE INVENTION
This invention relates to well jars generally and in particular to rotary
jars that allow the force required to trip the jars to be changed by
changing the torque in the jars.
Well jars are part of the drill string. Their purpose is to strike a sharp
blow upwardly or downwardly on the drill string as the drill string exerts
an upward or downward force on the portion of the string below the jars
that is stuck in the hole. Obviously, if the pipe string is stuck above
the jars, they cannot help free the pipe.
One of the most common causes of "Stuck Pipe" is differential pressure
sticking. This condition occurs when the hydrostatic head pressure of the
mud column exceeds the pressure in a formation that has been penetrated by
the well bore. This differential pressure can hold the pipe string against
the formation on one side of the well bore with a force great enough to
prevent longitudinal and rotational movement of the pipe relative to the
formation. Another common cause of stuck pipe are "key seats". These are
formed when the inclination of the well bore increases over a relatively
short distance, which can result in the drill string being pulled into
engagement with the high side of the well bore.
A drill string includes a "bottom hole assembly", which consists of the bit
and whatever number of drill collars and joints of heavyweight drill pipe
that are considered necessary to put weight on the bit. Rotary jars are
normally run at the top of the bottom hole assembly since the large
diameter drill collars and drill pipe are most likely to stick. When the
drilling assembly becomes stuck, the driller uses the jars to apply sharp
upward and downward forces to the assembly to help free it. Jars are
normally set to trip when an upward force is exerted on the jars that is
about 20,000 to 30,000 pounds more than the weight of the drill pipe above
the jars or a downward force of about 20,000 to 30,000 pounds is exerted
on the jars using the weight of the drill pipe.
In recent years, the practice of running 18 to 27 thirty foot drill collars
has changed to a combination of a few collars and several joints of
heavyweight drill pipe. This practice is especially prevalent in highly
deviated well bores where drill pipe sticking is most likely to occur.
Under the former practice, drilling jars were run just above the top drill
collar and always in the neutral tension/compression position to protect
the jars from excessive compressive or tensile stress. With the advent of
heavyweight drill pipe, it is still necessary to run the jars in the
neutral position, therefore, jar placement is normally above the last
joint of heavyweight pipe.
Common practice is to run 900 to 1,500 feet of heavyweight pipe above one
stand (three 30') drill collars. Under these conditions, using three 8"
drill collars, 1,500 feet of five inch heavyweight pipe and 20,000 pounds
of over pull the heavyweight pipe will stretch 3" at the jars and 10,000
feet of 5" drill pipe will stretch 55 inches at the rig floor. As the jars
trip (release all weight beneath the jars) the mandrel is pulled upwardly
at a high velocity because of the potential energy stored in the stretched
drill pipe. The heavyweight pipe also has stored potential energy due to
the three inches of stretch and accelerates downward rapidly. The jar
mandrel accelerating upwardly strikes the jar anvil, which will be
accelerating downwardly, causing a sharp upward blow to be delivered to
the stuck portion of the pipe--the fish. However, since the mandrel and
the anvil impact while they are accelerating in opposite directions, the
force that will be transmitted to the fish will be the difference between
the upward force of the mandrel and the downward force of the anvil.
The jars of this invention operate on the principle described in U.S. Pat.
No. 3,208,541, U.S. Pat. No. 3,233,690, and U.S. Pat. No. 4,665,998, all
of which are incorporated herein by reference.
Basically, the jars described in the patents and the jar of this invention
include two telescoping members, an inner member (the mandrel) and an
outer member (the anvil). In the jars described in the '541 and '690
patents, the mandrel is provided with a plurality of notches that have
curved outwardly flaring sidewalls and longitudinally extending grooves. A
plurality of rollers are mounted on the inside of the anvil for moving
into and out of the notches and the grooves. When the rollers are in the
notches, the two telescoping members cannot move longitudinally relative
to each other. When the rollers are in the grooves, the two members can
move longitudinally relative to each other. Their movement longitudinally
is limited by impact shoulders and it is through the shoulders that the
potential energy stored in the drill pipe is transmitted to the stuck
drill string during the operation of the jar.
In the '998 patent, the grooves are on the inside wall of the anvil and the
rollers are mounted on the mandrel. This is the arrangement shown and
described in this specification.
To allow the build up of energy in the drill pipe, the rollers are held in
the notches by a spring. When the longitudinal force on the jars has a
horizontal force component due to the flared sidewalls of the notches that
is large enough to rotate the two members relative to each other and force
the rollers out of the notches, the jar trips and the two members move
relative to each other with great velocity until the impact shoulders on
the members meet. The impact of the shoulders meeting produces a sharp
blow on the drill string. The amount of energy transmitted to the drill
string depends upon the potential energy stored in the drill string as the
jar is tripped. The amount of longitudinal force required to trip the jar
depends upon the spring force resisting the lateral movement of the
rollers and the angle that the sides of the notches make with the
horizontal, which determine the horizontal component produced by a given
longitudinal force. The upward or downward force required to trip the jars
can be adjusted by applying torque to the drill string. Torque in one
direction will assist the spring and require a greater force to trip the
jars. Torque in the opposite direction will decrease the force required.
It is the object of this invention to improve upon a rotary jar of the type
described above by providing serpentine (sine wave) shaped grooves in the
mandrel through which the rollers travel when the jar is tripped to
transmit torque to the fish (the stuck section of the drill string) urging
the fish to rotate clockwise and then counterclockwise to assist in
breaking the seal between the fish and the well bore in the case of
differential pressure sticking.
It is yet another feature of this invention to convert the potential energy
in the drill string at the time the jars are tripped into a torsional
force that reverses direction urging the fish to rotate back and forth.
As the rollers move upwardly along the sine wave grooves, they will also
move laterally first counterclockwise and then clockwise and a huge
angular acceleration will be imparted to both the upper and lower drill
strings. As this is real motion involving a large mass, large angular
momentum is imparted to these members. Contrary to a conventional jar
where the kinetic energy of the mandrel is dissipated in a fraction of a
second, the angular momentum will occur over a significant period of time
and will traverse both upper and lower sections of the drill string at a
high speed. The rotational motion will be damped as the wave progresses
away from the jars, but the magnitude of the degree of rotation and the
time in which it occurs is a function of the frequency and amplitude of
the sine wave grooves. These are controllable variables machined into the
design. There is a large surplus of available potential energy in the
stretched drill string which is mostly wasted in conventional jars due to
the nullifying effect of the downward acceleration of the drill string
beneath the jars, and the fact that conventional jars only impart linear
motion. By converting a large portion of the available potential energy
stored in the stretched drill string to torque thereby rotating the lower
and upper sections the jars ability to break the seal between the fish and
the wall cake, thereby equalizing the pressure around the fish and freeing
the pipe, is greatly increased. This is especially important when trying
to free drill pipe in high angle holes.
The rotational motion produced by the serpentine grooves is transmitted to
the drill string above the jars as well and this torque initially is in
the direction to break the threaded connections between the drill pipe.
Therefore, it is another object and feature of this invention to provide a
torque dissipating sub assembly for connecting in the drill string above
the mandrel to prevent rotational motion from being transmitted tot he
tool joints above the jars in the drill string. The sub assembly can
reduce or eliminate the rotational motion by using mechanical means to
convert the kinetic energy to either thermal energy through friction or to
potential energy through a resistive spring force. The continued
application of torque to the fish as the jar is tripped over and over
should increase the chances of freeing the fish.
These and other objects, advantages, and features of the invention will be
apparent to those skilled in the art from reading this specification
including the attached drawings and appended claims.
IN THE DRAWINGS
FIG. 1 is a vertical, sectional view through the preferred embodiment of
the well jar of this invention.
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1.
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1.
FIG. 4 is a vertical, sectional view on an enlarged scale of the portion of
the jar in FIG. 1 where the cam plates and rollers are located.
FIG. 5 is a view taken along line 5--5 of FIG. 4.
FIG. 6 is a cross-sectional view through one of the roller assemblies
attached to the inner member of the jar.
FIG. 7 is a plan view of the grooves through which the rollers travel when
the jar is tripped.
FIG. 8 is a sectional view of a torque dissipating sub assembly which can
be used to prevent the transmission of torque to the still string above
the jar.
FIGS. 8A and 8B, respectively, are end views of a clutch disc and a clutch
plate used in the torque dissipating sub of FIG. 8.
FIG. 9 is a sectional view of an alternative torque dissipating sub
assembly which can be used to prevent the transmission of torque to the
drill string above the jar.
The jar includes outer member 10 (the anvil) and inner member 11 (the
mandrel) that are movable longitudinally relative to each other a limited
distance. In FIG. 1, these tubular members are shown in one piece whereas
they are actually made up of a number of tubular sections connected
together by threads for ease of machining assembly and repair or
replacement of worn or broken parts of the jar. Mandrel 11 is provided
with appropriate threads (not shown) for connecting the mandrel to the
drill string extending between the jar and the surface. Anvil 10 has
threads 12 on its lower end for connecting the anvil to the fishing tool
or the portion of the drill string extending below the jar. This is the
usual arrangement. The roles of the two members could be reversed, if
desired.
The distance the members can move longitudinally relative to each other is
limited by annular shoulders on the members. When the jar is in use, the
anvil will be connected to the stuck pipe and will move only as far as the
pipe between the jar and the fish is stretched. Therefore, it is the
mandrel that moves relative to the anvil during a jarring operation. As
the mandrel moves downwardly, its travel is limited by the engagement of
downwardly facing shoulder 14 on the mandrel and upwardly facing shoulder
16 on the anvil. Upward movement is limited by downwardly facing shoulder
18 on the anvil and upwardly facing shoulder 20 on the mandrel. In
operation, as explained above, these shoulders come together with great
force due to the energy stored in the drill pipe before the jar is
tripped.
In this embodiment, the jar can jar both up and down. Holding means are
provided to hold the mandrel and anvil from relative movement while energy
is being stored in the drill string. In the embodiment shown, the holding
means includes three cam plates 22, 24, and 26 that are laterally spaced
around the inner surface of the anvil. As shown in FIGS. 2 and 3, they are
arcuate in cross-section to fit the curvature of the inner surface. The
cam plates are held in position by a plurality of cap screws 28 that
extend through openings provided in the wall of the anvil to engage tapped
holes in the cam plates. To position the cam plates to receive the cap
screws, locator pins 30, are positioned in openings in the sidewall of the
anvil 10 to engage a non-tapped locating hole at the upper end of each cam
plate. These pins align the tapped holes in the plates with the openings
in the sidewall of the anvil to insure that the cam plates are properly
positioned relative to each other on the inside wall of the anvil. These
locator pins are shown in FIG. 2.
Each cam plate has a plurality of U-shaped notches, as best seen in FIG. 4
where the mandrel is broken away to show cam plate 22 in elevation. In
this embodiment, two longitudinally spaced sets of three notches each are
used. The upper set is made up of notches 32. The lower set is made up of
notches 38. The notches open outwardly in a lateral direction with
diverging curved sidewalls.
A plurality of rollers are located on the outer surface of the mandrel to
engage the notches and hold the mandrel from longitudinal movement
relative to the anvil. When the rollers are out of engagement with the
notches and positioned in the longitudinal extending spaces between the
cam plates, as shown in FIG. 5, where upper rollers 44 and lower rollers
49, (only one of which is shown in FIG. 7) are positioned in between cam
plates 22, 24, and 26, the mandrel can move longitudinally relative to the
anvil. The rollers are attached to the outer surface of the mandrel in two
spaced groups of three. They are spaced vertically as shown in FIG. 4 so
the rollers in one group engage upper notches 32 and the other group of
rollers engage lower notches 38.
The two groups of rollers are spaced longitudinally and the spaces between
the cam plates through which they travel are designed for the rollers of
each group to be longitudinally in alignment with the longitudinal axis of
the jar as they move through the spaces between the plates.
A typical roller assembly is shown in FIG. 6. It includes shaft 50 and cap
screw 52 that attaches the roller assembly to mandrel 11. Shaft 50 has
cylindrical surface 54 upon which roller 56 is mounted for rotation
relative to shaft 50. To assemble the roller on the shaft, cylindrical
surface 54 extends outwardly to the end of the shaft. The roller is moved
into position over the cylindrical surface and then the end of the shaft
is upset to form retaining ring 58 to hold the roller on the shaft while
allowing the roller to freely rotate relative to the shaft.
In order to relieve cap screw 52 of as much of the stress imposed on shaft
50 by roller 56, the inner end of shaft 50 is cup-shaped to provide
annular section 60 that extends into annular recess 62 in the sidewall of
inner member 11. By designing annular section 60 of the shaft so that
there is little clearance between the walls of the annular section and the
walls of the recess, a portion of the reaction forces required to resist
the load imposed on the shaft by the roller are transmitted directly to
the mandrel through annular section 60.
To hold the rollers in engagement with the notches, two torsion springs 64
and 66 are positioned at the lower end of the jar. The upper end of each
spring is connected to the mandrel through pins 68 and 70. These pins
engage keyways 72 and 74 that extend along the outer surface of the
mandrel so that the spring can exert a torque on the mandrel but still
allow relative movement of the mandrel relative to the springs. The lower
end of each spring is connected to the anvil through pins 76 and 78.
Torque is imposed on the mandrel by rotating the mandrel relative to the
anvil a desired distance and then inserting the pins. The torque
constantly urges the mandrel to rotate in a direction to move the rollers
into the notches. The amount of torque imposed on the mandrel determines
at what upward or downward force the jar will trip. Also entering into the
determination of when the jar will trip is the angle of the top and bottom
sides of the notches. They do not have to be the same. The notches could
be arranged to trip at a lesser force on a down jar then on an up jar, if
desired.
As explained above, it is a feature of this invention that the
longitudinally extending spaces between cam plates 22, 24, and 26 are
sinusoidal as shown in FIG. 7 where the sinusoidal space between plates 22
and 24 is shown. This causes the rollers to impose torque on the fish,
first in one direction and then the other direction as the rollers travel
along the spaces between the cam plates. If this torque causes the fish to
rotate, it should help in freeing the fish.
It is important that the torque imposed on the drill string below the jar
rotate the string in a direction to make up the tool joints in the string.
This results, however, it the torque on the drill string above the jar
tending to unscrew the tool joints. Thereby, torque dissipating assembly
80 is placed in the string immediately above the drilling jar.
Torque dissipation assembly 80 of FIG. 8 includes inner tubular member 82
that is connected to the jar mandrel and outer sleeve 84 that is connected
to the drill string above the jars by tool joint 87. The inside diameter
of a portion of tubular member 82 is reduced to forum annular cavity 83
between member 82 and sleeve 84. A plurality of clutch disks 86 and clutch
plates 88 are positioned alternately in annular cavity 83. The clutch
plates and the clutch disks are compressed around member 82 to prevent
relative rotation of the member and the sleeve. The clutch disks and
plates are compressed with sufficient force to hold member 82 and outer
sleeve 84 in fixed arrangement without slippage during normal drilling
operations. However, when the drilling jar is tripped, the torque
generated by the jar exceeds the compression force of the clutch disks and
plates and the inner member rotates relative to the outer sleeve. This
slippage allows the torsional energy of the jar to be converted to thermal
energy as friction occurs between the clutch and the inner tubular member
82. Further, spring loaded pin 88 provides a positive means of providing
rotation of the drill string should the clutch disks and plates become so
worn that they are no longer able hold member and sleeve 84 in fixed
arrangement.
FIG. 9 shows alternative torque dissipation assembly 90 which includes
resilient means, preferably torsional spring 96, for absorbing the upward
torsional energy generated by the jar. Assembly 90 comprises inner and
outer tubular members 92 and 94. The lower end of torsional spring 96 is
connected to inner tubular member 92 by pin 97 while the upper end is
connected to outer tubular member 94 by pin 98. During normal drilling
operations right hand torque causes the inside diameter of spring 96 to
decrease and grip tubular member 92 with sufficient force to transmit
torque to this drill string below. When torque is transmitted upward from
the jar, spring 96 moves out of frictional engagement with tubular member
92 allowing rotation relative to tubular member 94, absorbing the
rotational energy and converting it to potential energy. This potential
energy is then converted back to rotational motion as the spring imposes
an oppositely directed torque on the mandrel of the drilling jar. Should
spring 96 break or become separated from either the inner or outer tubular
member, assembly 90 is provided with spring loaded pin 99 which limits the
free relative rotation of the tubular members to 350.degree..
The above described torque dissipating assemblies are particularly useful
for use with jars that generate torque in a single direction unlike the
jar described above. The jar described above imposes torque alternately
between a clockwise direction and counterclockwise direction due to the
sinusoidal nature of the longitudinally extending spaces between the cam
plates of the jar. It is anticipated that these complementary forces will
tend to eliminate any tendency to back off the threaded connections in the
string.
From the foregoing it will be seen that this invention is one well adapted
to attain all of the ends and objects hereinabove set forth, together with
other advantages which are obvious and which are inherent to the apparatus
and structure.
It will be understood that certain features and subcombinations are of
utility and may be employed without reference to other features and
subcombinations. This is contemplated by and is within the scope of the
claims.
Because many possible embodiments may be made of the invention without
departing from the scope thereof, it is to be understood that all matter
herein set forth or shown in the accompanying drawings is to be
interpreted as illustrative and not in a limiting sense.
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